This invention relates generally to controllable fins for vehicles operable in a fluid medium and more particularly to a self-actuating controllable fin which requires no external mechanical hardware.
The path of conventional guided missiles, guided projectiles, torpedos, submarines and the like is usually controlled by mechanically changing the angle of attack of a set of shaft-mounted metal fins in response to a servo-control signal generated by the vehicle's guidance and control system. In this manner aerodynamic or hydrodynamic lift is obtained which provides the forces necessary to alter the path of the vehicle as desired. In order to achieve maximum agility in a high speed vehicle the utilization of sophisticated, costly, and complex electrohydraulic servo-actuators is most often prescribed.
The modern guided projectile, which must be launched at high velocity from a gun barrel, is severely volume and weight limited as compared to a guided missile. The chief objective of any guided projectile is to critically damage the target, but as more volume is taken up by seeker and fuze, guidance and control assemblies, rocket motor, etc. there is less volume available for the warhead. This imposes a critical constraint on the design and placement of control surfaces and their associated actuator subassemblies.
For example, current guided projectiles employ rocket propulsion to maintain velocity and enhance maneuverability during the terminal portion of the trajectory. Folding tailfins are used for aeroballistic stability, and forward canard fins are employed for guidance and control. From the standpoint of economy and design simplicity it would be desirable to have the rear stabilizing fins also function as the guidance and control surfaces. But this approach is not technically feasible with current technology because there is not enough room available in the rear portion of the projectile to accommodate both the rocket motor and fin actuation components.